Alcohol, Health, and Causality

All right, let's have the good news first: if you are a moderate alcohol drinker, you are on average healthier than heavy or non-drinkers. Now the bad news: you may not be healthier because you drink alcohol moderately.

Causality is a funny thing. Sometimes we think we can see a the flow of causation simply because we see an association. And so since doctors have, study after study, seen an association between health and moderate alcohol consumption, they have jumped to the conclusion that one begets the other. But what if they have it backward? That's a hypothesis in today's second-most popular story in the New York Times.

It may be that moderate drinking is just something healthy people tend to do, not something that makes people healthy.

“The moderate drinkers tend to do everything right — they exercise, they don’t smoke, they eat right and they drink moderately,” said Kaye Middleton Fillmore, a retired sociologist from the University of California, San Francisco, who has criticized the research. “It’s very hard to disentangle all of that, and that’s a real problem.”

The article cleverly turns the question around, looking not at the drinkers, but the non-drinkers.

Some researchers suspect the abstainer group may include “sick quitters,” people who stopped drinking because they already had heart disease. People also tend to cut down on drinking as they age, which would make the average abstainer older — and presumably more susceptible to disease — than the average light drinker....

Dr. Naimi of the C.D.C., who did a study looking at the characteristics of moderate drinkers and abstainers, says the two groups are so different that they simply cannot be compared. Moderate drinkers are healthier, wealthier and more educated, and they get better health care, even though they are more likely to smoke. They are even more likely to have all of their teeth, a marker of well-being.

“Moderate drinkers tend to be socially advantaged in ways that have nothing to do with their drinking,” Dr. Naimi said. “These two groups are apples and oranges.” And simply advising the nondrinkers to drink won’t change that, he said.

I have no horse in this race. It's good enough for me to know that moderate drinking--a beer or two--does not jeopardize my health. If it turns out it doesn't help it, either, c'est la vie.